Discovery of twin kHz quasi-periodic oscillations in the high galactic la titude X-ray transient XTE J2123--058

Abstract

We report the discovery of twin kHz quasi-periodic oscillations (QPOs) in the persistent X-ray flux of the new X-ray transient XTE J2123-058. We detected the QPOs in data taken with the proportional counter array on board the Rossi X-ray Timing Explorer on 1998 July 14, when the source count rate was at about 50% of its outburst peak level. The frequencies of the QPOs were 853+/-4 Hz and 1129+/-8 Hz. The peaks had widths of 32 (+11/-8) Hz and 50 (+17/-13) Hz and the rms amplitudes were 6.1% (+0.7/-0.6) and 6.5% (+0.9/-0.8), respectively. The QPO frequencies increased marginally with count rate and the amplitudes showed a small increase with photon energy. On the basis of the appearance in the color-color and hardness-intensity diagrams, the low-frequency power spectrum, and the strength of the kHz QPOs, the system can be classified as an atoll source. The source showed five type I X-ray bursts. The distance to the source is estimated to be about 10 (5-15) kpc, which combined with the high Galactic latitude of 36.2 degrees indicates the source is a located in the Galactic halo.

8 pages with 4 figures included, accepted for publication in ApJ Letters

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Cited by in corpus (18)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Millisecond Oscillations in X-Ray Binaries
• The distances to Galactic low-mass X-ray binaries: consequences for black hole luminosities and kicks
• Investigating stellar-mass black hole kicks
• Detecting gravitational wave emission from the known accreting neutron stars
• The distribution of kHz QPO frequencies in bright LMXBs
• Optical and X-ray observations of the neutron star soft X-ray transient XTE J1709-267
• Modelling the spin equilibrium of neutron stars in LMXBs without gravitational radiation
• Simultaneous Measurements of X-Ray Luminosity and Kilohertz Quasi-Periodic Oscillations in Low-Mass X-Ray Binaries
• The Low Quiescent X-Ray Luminosity of the Neutron Star Transient XTE J2123-058
• VLT spectroscopy of XTE J2123-058 during quiescence
• Optical studies of the X-ray transient XTE J2123-058 - II. Phase-resolved spectroscopy
• Investigation of the emission radii of kHz QPOs for the accreting millisecond X-Ray pulsars, Atoll and Z sources
• XTE J2123-058: A New Neutron Star X-Ray Transient
• Rotational Broadening Measurement for the Neutron Star X-Ray Transient XTE J2123-058
• Statistical properties of twin kHz QPO in neutron star LMXBs
• Keck Measurement of the XTE J2123-058 Radial Velocity Curve
• A Study of the New X-ray Transient RXTE J2123-058 during its Post-Outburst State